arXiv:1005.1704 · Physical Review B
Coefficients of bosonized dimer operators in spin- 12 XXZ chains and their applications
Shintaro Takayoshi, Masahiro Sato
Abstract
Comparing numerically evaluated excitation gaps of dimerized spin-$\frac{1}{2}$ $XXZ$ chains with the gap formula for the low-energy effective sine-Gordon theory, we determine coefficients ${d}_{xy}$ and ${d}_{z}$ of bosonized dimerization operators in spin-$\frac{1}{2}$ $XXZ$ chains, which are defined as ${(\ensuremath{-}1)}^{j}({S}_{j}^{x}{S}_{j+1}^{x}+{S}_{j}^{y}{S}_{j+1}^{y})={d}_{xy}\text{ }\text{sin}[\sqrt{4\ensuremath{\pi}}\ensuremath{\phi}(x)]+\ensuremath{\cdots}$ and ${(\ensuremath{-}1)}^{j}{S}_{j}^{z}{S}_{j+1}^{z}={d}_{z}\text{ }\text{sin}[\sqrt{4\ensuremath{\pi}}\ensuremath{\phi}(x)]+\ensuremath{\cdots}$. We also calculate the coefficients of both spin and dimer operators for the spin-$\frac{1}{2}$ Heisenberg antiferromagnetic chain with a nearest-neighbor coupling $J$ and a next-nearest-neighbor coupling ${J}_{2}=0.2411J$. As applications of these coefficients, we present ground-state phase diagrams of dimerized spin chains in a magnetic field and antiferromagnetic spin ladders with a four-spin interaction. The optical conductivity and electric polarization of one-dimensional Mott insulators with Peierls instability are also evaluated quantitatively.